Messages in this thread | | | From | Amir Goldstein <> | Date | Mon, 6 Feb 2023 22:06:34 +0200 | Subject | Re: [PATCH v3 0/6] Composefs: an opportunistically sharing verified image filesystem |
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On Mon, Feb 6, 2023 at 9:32 PM Miklos Szeredi <miklos@szeredi.hu> wrote: > > On Mon, 6 Feb 2023 at 18:16, Amir Goldstein <amir73il@gmail.com> wrote: > > > it's not overlay{erofs+erofs} > > it's overlay{erofs+ext4} (or another fs-verity [1] supporting fs) > > the lower layer is a mutable fs with /objects/ dir containing > > the blobs. > > > > The way to ensure the integrity of erofs is to setup dm-verity at > > erofs mount time. > > > > The way to ensure the integrity of the blobs is to store an fs-verity > > signature of each blob file in trusted.overlay.verify xattr on the > > metacopy and for overlayfs to enable fsverity on the blob file before > > allowing access to the lowerdata. > > > > At least this is my understanding of the security model. > > So this should work out of the box, right? >
Mostly. IIUC, overlayfs just needs to verify the signature on open to fulfill the chain of trust, see cfs_open_file(): https://lore.kernel.org/linux-fsdevel/9b799ec7e403ba814e7bc097b1e8bd5f7662d596.1674227308.git.alexl@redhat.com/
Thanks, Amir.
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